1. Field of the Invention
The present invention relates generally to data storage, and in particular to using selective attribute acquisition and clause evaluation for policy based data storage management.
2. Background Information
As the amount of data generated and stored persistently grows exponentially, automatically managing the data (e.g., information lifecycle management, archive and backup, etc.) has become more challenging.
One technique used for an automated data management system is the use of policy-based management. Policy-based data management is based on a set of policies (rules), which comprise conditions and actions. An example of a rule is: if the last access time is older than 30 days (condition), then archive the file (action). Such a management system evaluates the rule condition on managed data objects (i.e., rule evaluation), and then applies the action to these objects on which the condition is satisfied (i.e., rule apply).
Because the rule condition usually compares metadata or content attributes of data objects with certain values, the rule evaluation includes the acquisition (e.g., crawling or mining) of those attributes, as well as the condition evaluation. Due to the instability of many attributes, conventional management systems must acquire attributes and perform evaluations repeatedly on all data objects. This introduces prohibitive overhead when dealing with a large number (e.g., millions) of data objects, especially when the rule uses content attributes, which are usually much more costly and obtained from very expensive mining operations.